Ashraf Tadross
National Research Institute Of Astronomy And Geophysics Nriag, Astronomy, Department Member
- Prof. Ashraf Latif TadrossHead of Astronomy Department. Professor of Star Clusters and Galactic Structure. National Research Institute of Astronomy and Geophysics, Cairo, Egypt.edit
Research Interests: Physics and Open cluster
The astrophysical parameters of four unstudied open star cluster candidates; Ivanov 2, 7, 9, and Harvard 9; have been estimated for the first time using the PPMXL database. The stellar density distributions and color-magnitude diagrams... more
The astrophysical parameters of four unstudied open star cluster candidates; Ivanov 2, 7, 9, and Harvard 9; have been estimated for the first time using the PPMXL database. The stellar density distributions and color-magnitude diagrams for each cluster are used to determine the geometrical structure (cluster center, limited radius, core and tidal radii, the distances from the Sun, from the Galactic center and from the Galactic plane). Also, the main photometric parameters (age, distance modulus, color excesses, membership, total mass, relaxation time, luminosity and mass functions) are estimated.
The main aim of this paper is to study the astrophysical behaviour of open clusters' properties along the Milky Way Galaxy. Near-IR JHKs (2MASS) photometry has been used for getting a homogeneous Catalog of 263 open clusters' parameters,... more
The main aim of this paper is to study the astrophysical behaviour of open clusters' properties along the Milky Way Galaxy. Near-IR JHKs (2MASS) photometry has been used for getting a homogeneous Catalog of 263 open clusters' parameters, which are randomly selected and studied by the author through the last five years; most of them were studied for the first time. The correlations between the astrophysical parameters of these clusters have been achieved by morphological way and compared with the most recent works.
We present here our first series in studying the astrophysical parameters of the open cluster "Ruprecht 15" using PPMXL1 database. In this context, the photometric, astrometry and statistical parameters for this cluster (limited radius,... more
We present here our first series in studying the astrophysical parameters of the open cluster "Ruprecht 15" using PPMXL1 database. In this context, the photometric, astrometry and statistical parameters for this cluster (limited radius, core and tidal radii, distances, membership, reddening, age, luminosity function, mass function, total mass, and the dynamical relaxation time) are determined for the first time.
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We studied the principal parameters of some previously unstudied open star clusters using the JHK Near-IR photometry (2MASS survey). These clusters have been selected from the updated Catalogs of Dais and Webda. Based on the 2MASS... more
We studied the principal parameters of some previously unstudied open star clusters using the JHK Near-IR photometry (2MASS survey). These clusters have been selected from the updated Catalogs of Dais and Webda. Based on the 2MASS database and the DSS visual images, some homogeneous methods and algorithms have been applied. The astrometry and photometric principal parameters are determined for the first time.
A deep photometric analysis in the open star cluster NGC 1883 has been presented here and added to the work of Carraro et al. (2003), which is the only previous work introduced for this cluster. The radius and metallicity have been... more
A deep photometric analysis in the open star cluster NGC 1883 has been presented here and added to the work of Carraro et al. (2003), which is the only previous work introduced for this cluster. The radius and metallicity have been re-estimated in the present work. In addition, new parameters, namely luminosity function, mass function, total mass, mass segregation and the relaxation time of the cluster NGC 1883 have been estimated here for the first time.
The main physical parameters; the cluster center, distance, radius, age, reddening, and visual absorbtion; have been re-estimated and improved for the open cluster NGC 7086. The metal abundance, galactic distances, membership richness,... more
The main physical parameters; the cluster center, distance, radius, age, reddening, and visual absorbtion; have been re-estimated and improved for the open cluster NGC 7086. The metal abundance, galactic distances, membership richness, luminosity function, mass function, and the total mass of NGC 7086 have been examined for the first time here using Monet et al. (2003) catalog.
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A deep stellar analysis is introduced for the poorly studied open cluster NGC 2509. The Near-IR database of the digital Two Micron All Sky Survey (2MASS) has been used to re-estimate and refine the fundamental parameters of the cluster,... more
A deep stellar analysis is introduced for the poorly studied open cluster NGC 2509. The Near-IR database of the digital Two Micron All Sky Survey (2MASS) has been used to re-estimate and refine the fundamental parameters of the cluster, i.e. age, reddening, distance, and diameter. As well as, luminosity function, mass function, total mass, relaxation time, and mass segregation of NGC 2509 have been estimated here for the first time.
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A sample of 145 JHK--2MASS observations of NGC open star clusters is studied, of which 132 have never been studied before. Twelve are classified as non-open clusters and 13 are re-estimated self-consistently, after applying the same... more
A sample of 145 JHK--2MASS observations of NGC open star clusters is studied, of which 132 have never been studied before. Twelve are classified as non-open clusters and 13 are re-estimated self-consistently, after applying the same methods in order to compare and calibrate our reduction procedures. The fundamental and structural parameters of the 120 new open clusters studied here are derived using color-magnitude diagrams of JHK Near-IR photometry with the fitting of solar metallicity isochrones. We provide here, for the first time, a catalog of the main parameters for these 120 open clusters, namely, diameter, distance, reddening and age.
Research Interests: Astrometry and Stars
The photometric data of Kalużny (1988) was used in conjunction with the proper motion measurements of USNOB1.0 catalog (Monet et al. 2003) to refine and complete the main physical properties of the faint open cluster NGC 1193. (© 2004... more
The photometric data of Kalużny (1988) was used in conjunction with the proper motion measurements of USNOB1.0 catalog (Monet et al. 2003) to refine and complete the main physical properties of the faint open cluster NGC 1193. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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A morphological analysis has been presented as a completed work for estimating the most physical properties of open star cluster NGC 7296. For this purpose, near-IR database of the digital Two Micron All Sky Survey (2MASS) has been used.... more
A morphological analysis has been presented as a completed work for estimating the most physical properties of open star cluster NGC 7296. For this purpose, near-IR database of the digital Two Micron All Sky Survey (2MASS) has been used. Center, radius, membership, distances, reddening, age, metallicity, luminosity and mass functions, total mass, mass segregation and the dynamical relaxation time of the cluster have been estimated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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The fundamental parameters of 60 previously unstudied open clusters of Czernik, Dol-Dzim, Kronberger, and Turner were derived with color-magnitude diagrams of JHK s Near-IR 2MASS photometry. These clusters have never been studied before,... more
The fundamental parameters of 60 previously unstudied open clusters of Czernik, Dol-Dzim, Kronberger, and Turner were derived with color-magnitude diagrams of JHK s Near-IR 2MASS photometry. These clusters have never been studied before, and we provide, for the first time, the cluster parameters; the angular diameter, distance, reddening, age, and metallicity. The 2MASS catalog has the advantages of being homogeneous database, enabling us to observing the young clusters in their dusty environments and reaching their outer regions where the low mass stars dominate.
Research Interests: Astrometry and Stars
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A sample of 160 UBVCCD observations of open star clusters near the galactic plane has been studied, and a catalogue of their properties obtained. The main photometrical properties have been re-estimated self consistently and the results... more
A sample of 160 UBVCCD observations of open star clusters near the galactic plane has been studied, and a catalogue of their properties obtained. The main photometrical properties have been re-estimated self consistently and the results have been compared with those of Lynga [Lynga, G., 1987. Catalog of Open Cluster Data, 5th Edition, Stellar Data Centers, Observatoire de Strasbourg, France].
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This paper is a continuation of a series, aiming to determine the main parameters of rarely or un-studied open star clusters using Near-IR JHK photometry. Cluster center coordinates, angular diameter, distances, reddening, age, and... more
This paper is a continuation of a series, aiming to determine the main parameters of rarely or un-studied open star clusters using Near-IR JHK photometry. Cluster center coordinates, angular diameter, distances, reddening, age, and metallicity are estimated for 25 un-studied open clusters, most of them in the first quadrant. A morphological analysis of 2MASS database (the digital “Two Micron All Sky Survey”) has been used.
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We present here the fundamental properties of some newly discovered open star clusters (Teutsch 144, Alessi 53, Riddle 4 and Juchrt 12) using the JHK Near-IR photometry (2MASS survey) of Cutri et al. (2003). These clusters have been... more
We present here the fundamental properties of some newly discovered open star clusters (Teutsch 144, Alessi 53, Riddle 4 and Juchrt 12) using the JHK Near-IR photometry (2MASS survey) of Cutri et al. (2003). These clusters have been selected from Kronberger et al. (2006) who presented some new discovered stellar groups on the basis of 2MASS photometry and the DSS visual images. The astrometry and photometric parameters are determined using the stellar density distributions and color-magnitude diagrams fittings. Center, radius, membership, distances, reddening, age, luminosity function, mass function, total mass, and the dynamical relaxation time have been estimated for the first time. This paper is a part of Reda's PhD project.
In this paper, we study the characteristics and physical properties of the young open cluster Pleiades (NGC 1432; M45; Melotte 22; Seven Sisters) using Near Infra Red, JHK pass bands. Our results have been compared with those found in... more
In this paper, we study the characteristics and physical properties of the young open cluster Pleiades (NGC 1432; M45; Melotte 22; Seven Sisters) using Near Infra Red, JHK pass bands. Our results have been compared with those found in optical, UBV, newly observations. The membership validity of some variable binary stars, which are Located in Taurus constellation, and their relation with Pleiades cluster have been achieved.
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The young open star cluster M25 (IC 4725) is located in the direction of the galactic center in a crowded region, near much irregular absorption features on Sagittarius arm. This cluster has some difficult observing problems due to its... more
The young open star cluster M25 (IC 4725) is located in the direction of the galactic center in a crowded region, near much irregular absorption features on Sagittarius arm. This cluster has some difficult observing problems due to its southern location. The mass data available in the literature have been gathered to reinvestigate this cluster using most photometric tools to determine its main photometric parameters. This system is found to be at a distance of 600 pc from the sun, of -52.82 pc from the galactic plane; and the median age is 9.45 x 10^(7) yr. More than 220 stars with mean reddening of 0.50 mag and absorption of 1.62 mag are found within the cluster.
From photoelectric observations of night sky brightness carried out at Abu-Simbel, Asaad et al. (1979) have obtained values of integrated starlight brightness at different Galactic latitudes. These data have been used in the present work... more
From photoelectric observations of night sky brightness carried out at Abu-Simbel, Asaad et al. (1979) have obtained values of integrated starlight brightness at different Galactic latitudes. These data have been used in the present work to obtain the brightness and color of the integrated starlight at North and South Celestial, Ecliptic and Galactic Poles. The present values of the brightness are expressed in S10 units and mag/arcsec2. Our results have been compared with that obtained by other investigators using photometric and star counts techniques. The B-V and B-R have been calculated and the results are compared with that obtained by other investigators.
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A search for discontinuity in the sky twilight brightness at different wavelengths and different solar depressions for altitudes 0, 5, 10, 30, 50 & 70 degrees is done. It is found that the logarithmic of difference in the brightness log... more
A search for discontinuity in the sky twilight brightness at different wavelengths and different solar depressions for altitudes 0, 5, 10, 30, 50 & 70 degrees is done. It is found that the logarithmic of difference in the brightness log (I1-I2) of two similar patches lying at solar and anti-solar verticals are not suffering of any discontinuity, when plotted versus sun's depression. Whatever, the ratio I1/I2 shows that there is discontinuity in the curves at altitudes less than or equal 30 degrees. While for altitudes 50 & 70 degrees slight patches of discontinuities have been detected. The phenomenon of discontinuities may be referred to the changes in the sky twilight brightness due to the effect of the Earth's shadow on diffusing and luminescent layers in the upper atmosphere.
The young open star cluster M25 (IC 4725) is located in the direction of the galactic center, near much irregular absorption features on Sagittarius arm. This system is found to be at a distance of 600 pc, with a median age of 9.45 × 107... more
The young open star cluster M25 (IC 4725) is located in the direction of the galactic center, near much irregular absorption features on Sagittarius arm. This system is found to be at a distance of 600 pc, with a median age of 9.45 × 107 years and a distance from the galactic plane of –52.82 pc The mass data available in the literature has been gathered and many statistical methods have been applied for this cluster. Depending only on these methods, the stellar density, the distribution of dark matter, the luminosity and the mass functions have been estimated. The center of the cluster has been defined, it is shifted by 45 arc sec in the northeast direction. The radius of the cluster is found to be 4 pc. More than 220 stars with mean reddening of 0.50 mag and absorption of 1.62mag are found inside this aria. The total mass of the cluster has been estimated with the mass of the interstellar matter (gas and dust). It is found to be 1937 M ⊙, whereas about 24% of the material mass of the cluster has remained as interstellar matter after the processes of formation.
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The Naval Observatory Merged Astrometric Dataset (NOMAD) contains astrometric and photometric data for over 1 billion stars derived from the Hipparcos, Tycho-2, UCAC2 and USNO-B1.0 catalogues for astrometry and optical photometry,... more
The Naval Observatory Merged Astrometric Dataset (NOMAD) contains astrometric and photometric data for over 1 billion stars derived from the Hipparcos, Tycho-2, UCAC2 and USNO-B1.0 catalogues for astrometry and optical photometry, supplemented by Two Micron All Sky Survey (2MASS) near-infrared photometry. For each unique star the 'best' astrometric and photometric data are chosen from the source catalogues and merged into a single dataset (cf. Zacharias et al., 2004, Cat. I/297). Using this data base; compared with the 2MASS of Cutri et al. (2003, Cat. II/246); we could determine the fundamental parameters of 24 (of 96) open clusters of Berkeley, which were never studied so far. (2 data files).
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The main astrophysical properties of 11 previously unstudied open star clusters are probed with JHK Near-IR (2MASS) photometry of Cutri et al. [Cutri, R., et al., 2003. The IRSA 2MASS All-sky Point Source Catolog, NASA/IPAC Infrared... more
The main astrophysical properties of 11 previously unstudied open star clusters are probed with JHK Near-IR (2MASS) photometry of Cutri et al. [Cutri, R., et al., 2003. The IRSA 2MASS All-sky Point Source Catolog, NASA/IPAC Infrared Science Archive] and proper motions (NOMAD) astrometry of Zacharias et al. [Zacharias, N., Monet, D., Levine, S., Urban, S., Gaume, R., Wycoff, G., 2004. American Astro. Soc. Meeting 36, 1418]. The fundamental parameters have been derived for IC (1434, 2156); King (17, 18, 20, 23, 26); and Dias (2, 3, 4, 7, 8), for which no prior parameters are available in the literature. The clusters’ centers coordinates and angular diameters are re-determined, while ages, distances, and color excesses for these clusters are estimated here for the first time.
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Depending mainly on UBVCCD data, the metallicities of 91 open star clusters nearby the galactic disk have been estimated using Cameron’s [A&A 147 (1985b) 39] method. The metallicity radial gradient along the galactic plane is found to be... more
Depending mainly on UBVCCD data, the metallicities of 91 open star clusters nearby the galactic disk have been estimated using Cameron’s [A&A 147 (1985b) 39] method. The metallicity radial gradient along the galactic plane is found to be −0.09 dex/kpc; which is in a very good agreement with Panagia and Tosi [A&A 96 (1981) 306] and Carraro et al. [MNRAS 296 (1998) 1045]. Vertically on the galactic disk, within about 800 pc, the metallicity gradient is found to be so trivial. An average age–metallicity relation has been examined, which confirms the previous suggestion that the metallicity of a cluster depending mainly on its position on the galactic disk more than its age.
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We use proper motion measurements to determine the real size and membership richness of a sample of open clusters located at high galactic latitudes (40 < |b| < 90).
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We present here the astrophysical parameters of three stellar open cluster candidates using PPMXL1 database. In this study, the main photometric, astrometry and statistical parameters of Ruprecht 13, Ruprecht 16 and Ruprecht 24 are... more
We present here the astrophysical parameters of three stellar open cluster candidates using PPMXL1 database. In this study, the main photometric, astrometry and statistical parameters of Ruprecht 13, Ruprecht 16 and Ruprecht 24 are estimated for the first time.
Research Interests: Astrometry and Stars
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The main astrophysical parameters of 24 previously unstudied open clusters of Berkeley catalogue are presented here. JHK near-infrared (Two Micron All Sky Survey) photometry and the proper motions astrometry of Naval Observatory Merged... more
The main astrophysical parameters of 24 previously unstudied open clusters of Berkeley catalogue are presented here. JHK near-infrared (Two Micron All Sky Survey) photometry and the proper motions astrometry of Naval Observatory Merged Astrometric Dataset (NOMAD) are used. The clusters' centres, angular diameters, ages, distances and colour excesses for these clusters are estimated for the first time.
Research Interests: Near Infrared and Surveys
A morphological analysis study of open clusters’ properties has been achieved for a sample of 160 UBVCCD open star clusters of approximately 128,000 stars near the galactic plane. The data was obtained and reduced from Tadross (2001)... more
A morphological analysis study of open clusters’ properties has been achieved for a sample of 160 UBVCCD open star clusters of approximately 128,000 stars near the galactic plane. The data was obtained and reduced from Tadross (2001) using the same reduction procedures, which makes this catalogue the largest homogeneous source of open clusters’ parameters.